1. Field
The aspects of the disclosed embodiments relate to a new way of recovering energy from the potential energy of water in a body of water. Particularly, the aspects of the disclosed embodiments relate to a method of generating hydroenergy, a hydroenergy generating plant, a use of the hydroenergy generating plant and a method of storing potential energy of water.
2. Brief Description of Related Developments
As a general rule, it is hard to store large amounts of electricity. Therefore energy is normally consumed at the same time it is produced. However, the demand for electricity varies over time. Typically there is lower demand for electricity during night time than day time. Common sources of alternative energy such as, for example, solar energy and wind energy, produce energy depending on the weather conditions and can be unpredictable and difficult to control. On the other hand, some production facilities such as nuclear power stations produce a mainly constant amount of energy practically all the time. Developing efficient ways of levelling peaks in electricity demand and storing electricity are therefore integral parts of development of energy systems of today.
Often, consumers are enticed to use more electricity at the low demand hours and less during peak hours in order to level the demand for electricity. For example many electricity companies are offering lower electricity prices for households during the night time than during the day time. There are hourly based electricity markets, e.g. the SPOT market in Nordic countries, with different electricity prices per hour depending on the supply and demand of the electricity. However, systems exist that attempt to vary electricity output or to store electricity in order to meet the varying demand.
In a hydroelectric power plant, water is led through turbines connected to electric generators to produce electricity. A common system of storing electricity is a hydro-pumped storage facility in which a hydroelectric power plant is connected to a water storage installation at a higher elevation. Electricity is stored as potential energy by pumping water to a higher elevation reservoir, such as a lake or a dam in a river, during low consumption of electricity. Thus, pumps are run with low-cost off-peak electric power. The water from the higher elevation reservoir is then used in the hydroelectric power plant at a lower elevation during high demand of electricity. The system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. This process, also called pumped storage hydroelectricity, is the most common form of grid energy storage used today.
There are numerous examples of pumped storage hydroelectricity systems. One example of such a system is described in U.S. Pat. No. 4,443,707.
The most advantageous and mostly used places for hydro-pumped storage facilities have traditionally been mountainous regions and already dammed rivers. Naturally, a vast demand for energy storage is present in other locations, as well. Although production of hydroelectricity can be considered as virtually non-polluting and renewable, building of new facilities is often considered as a great stress to nature. Also fluctuations in the water level in reservoirs normally have negative effects to the ecosystem.
Additionally, prior art such as WO2007/0009192 of Hastings et al. discloses a power generation system using array of water-containing vessels immersed in a large body of water to a substantial depth with the lower end of the vessel spaced above the water bed. A problem with such a system is control of buoyancy. As the vessel is emptied, there is significant force applied by the pressure of water to raise the vessel above the surface of the water.
It would be advantageous to efficiently handle both high and low demand and supply periods of electricity.
It would be advantageous to obtain a reliable, cost efficient and easy way of storing energy.
It would be advantageous to provide cost effective energy storing possibilities to new regions.
It would be advantageous to obtain an energy storage technology that improves the manageability, controllability, predictability and flexibility of supply and demand of electricity.